ASP.NET中随机生成验证码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Drawing;

public partial class CheckCode : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        DrawImage();
    }

    public static void DrawImage()
    {
        CheckCode7 img = new CheckCode7();
        int[] num = { 4, 5, 6 };
        Random random = new Random();
        int value = num[Convert.ToInt32(random.NextDouble() * 2)];
        HttpContext.Current.Session["CheckCode"] = img.RndNum(value);
        img.CreateImages(HttpContext.Current.Session["CheckCode"].ToString());
    }

    /// 
    /// 生成验证图片
    /// 
    /// 验证字符
    private void CreateImages(string checkCode)
    {
        int iwidth = (int)(checkCode.Length * 15);
        System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 25);
        Graphics g = Graphics.FromImage(image);
        g.Clear(Color.White);
        //定义颜色
        Color[] c = { Color.Tomato, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple, Color.Yellow, Color.Blue, Color.Wheat };
        //定义字体 
        string[] font = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体", "黑体", "楷体", "华文彩云", "隶书", "华文新魏", "华文黑细", "华文行楷" };
        Random rand = new Random();
        //随机输出噪点
        for (int i = 0; i < 120; i++)
        {
            int x = rand.Next(image.Width);
            int y = rand.Next(image.Height);
            g.DrawRectangle(new Pen(Color.LightSkyBlue, 0), x, y, 1, 1);
        }

        //输出不同字体和颜色的验证码字符
        for (int i = 0; i < checkCode.Length; i++)
        {
            int cindex = rand.Next(7);
            int findex = rand.Next(5);

            Font f = new System.Drawing.Font(font[findex], 12, System.Drawing.FontStyle.Bold
           | System.Drawing.FontStyle.Italic);
            Brush b = new System.Drawing.SolidBrush(c[cindex]);
            int ii = 4;
            if ((i + 1) % 2 == 0)
            {
                ii = 2;
            }
            g.DrawString(checkCode.Substring(i, 1), f, b, 3 + (i * 12), ii);
        }
        //画一个边框
        g.DrawRectangle(new Pen(Color.Orange, 0), 0, 0, image.Width - 1, image.Height - 1);

        //输出到浏览器
        System.IO.MemoryStream ms = new System.IO.MemoryStream();
        image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
        HttpContext.Current.Response.ClearContent();
        //Response.ClearContent();
        HttpContext.Current.Response.ContentType = "image/Jpeg";
        HttpContext.Current.Response.BinaryWrite(ms.ToArray());
        g.Dispose();
        image.Dispose();
    }

    /// 
    /// 生成随机的字母
    /// 
    /// 生成字母的个数
    /// string
    private string RndNum(int VcodeNum)
    {
        string Vchar = "1,2,3,4,5,6,7,8,9,0,a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z";
        string[] VcArray = Vchar.Split(',');
        string VNum = ""; //由于字符串很短，就不用StringBuilder了
        int temp = -1; //记录上次随机数值，尽量避免生产几个一样的随机数

        //采用一个简单的算法以保证生成随机数的不同
        Random rand = new Random();
        for (int i = 1; i < VcodeNum + 1; i++)
        {
            if (temp != -1)
            {
                rand = new Random(i * temp * unchecked((int)DateTime.Now.Ticks));
            }
            int t = rand.Next(VcArray.Length);
            if (temp != -1 && temp == t)
            {
                return RndNum(VcodeNum);
            }
            temp = t;
            VNum += VcArray[t];
        }
        return VNum;
    }
}

 

对应的前台页面中不用写任何代码，用时只要将图片路径设为此页面路径就可